(a) Technical Field
The present invention relates to a method for the preparation of 4,4′-dinitrodiphenylamine and 4,4′-bis(alkylamino)diphenylamine using a base catalyst complex.
(b) Background Art
4,4′-Dinitrodiphenylamine (4,4′-DNDPA) is easily reduced to 4,4′-diaminodiphenylamine (4,4′-DADPA) and is used as a source of an antioxidant in dyes and rubbers. Japanese Patent Application Publication No. H10-168038 discloses synthesis of 4,4′-DADPA by reducing 4,4′-DNDPA and describes that the 4,4′-DADPA compounds are excellent intermediates of additives for preventing oxidation and aging. As such, 4,4′-DADPA or 4,4′-DADPA derivatives are used as intermediates for additives of rubbers as well as dyes, agrichemicals and pharmaceuticals.
As a method for preparing 4,4′-DNDPA, nitration of N-acetyldiphenylamine followed by deacetylation is known. However, this method is problematic in that the nitration does not occur uniformly and separation by repeated recrystallization in alcohol is required. As another method, U.S. Pat. No. 4,990,673 discloses preparation of 4,4′-DNDPA by reacting 4-chloroaniline with an alkali metal cyanate. However, this method is problematic in that the reaction should be performed at 160° C. or above for at least 15 hours.
Also, a method of preparing DNDPA derivatives by reacting 4-nitroaniline (4-NA) with nitrobenzene derivatives is known [Bull. Chem. Soc. Jap., 1976, (1), p. 138-143]. In the reaction of 4-NA with the nitrobenzene derivative, a base such as potassium t-butoxide (t-BuOK) is used. Although it is described that ortho- and para-hydrogen-substituted and halogen-substituted products such as 2,4′-DNDPA, 4,4′-DNDPA, 5-chloro(bromo)-2,4′-dinitrodiphenylamin, etc. are prepared depending on the used base amount, the process of preparing 4-NA is required and it is not easy to prepare 4,4′-DNDPA selectively.
As a method of reacting 4,4′-DADPA with ketones, Great Britain Patent No. 1091376 describes a method of reacting 4,4′-DADPA with ketones to prepare 4-amino-4′-alkylaminodiphenylamines at high temperature and high pressure in the presence of a precious metal catalyst, and Japanese Patent Publication No. H10-219243 describes reaction of 4,4′-DADPA with ketones to prepare 4,4′-bis(alkylamino)diphenylamine (4,4′-BAADA). However, 4,4′-DNDPA has to be converted to 4,4′-DADPA before reaction with ketones and it is not easy to prepare pure 4,4′-DADPA.
The recently known nucleophilic aromatic substitution for hydrogen (NASH) reaction is advantageous in that harmful substances or difficult-to-remove intermediates are not generated since amines or amides are directly reacted with nitrobenzene or nitrobenzene derivatives in the presence of a base catalyst.
A method of directly reacting aniline and nitrobenzene in the presence of a base such as tetramethylammonium hydroxide (TMAH) to prepare 4-nitrodiphenylamine (4-NDPA), 4-nitrosodiphenylamine, etc. is known [J. Am. Chem. Soc., 1992, 114(23), 9237-8, U.S. Pat. Nos. 5,117,063, 5,252,737 , 5,331,099, 5,453,541, 5,552,531, 5,633,407].
And, U.S. Pat. Nos. 5,436,371, 5,380,407 and PCT Application Publication No. WO 93/24447 describe a method of synthesizing N-(4-nitrophenyl)benzamide by the NASH reaction using benzamide instead of aniline. It is described that nitrobenzene and benzamide are used at a molar ratio of about 1:1 to synthesize N-(4-nitrophenyl)benzamide, and then 4-NA is prepared therefrom by hydrolysis using water or ammonia. However, production of 4,4′-DNDPA is not mentioned in these patents, because the N-(4-nitrophenyl)benzamide resulting from the reaction of benzamide with nitrobenzene is stable and separable, and does not react further with nitrobenzene.
The inventors of the present invention have proposed in Korean Patent Application Publication No. 2001-0054045 a method of preparing 4,4′-DNDPA by the NASH reaction using urea and excess nitrobenzene, and then hydrogenating the 4,4′-DNDPA with a ketone in the presence of hydrogen and a hydrogenation catalyst to prepare 4,4′-BAADA in high yield and purity. However, due to the difficulty in recovering and recycling the base catalyst, the method is commercially uneconomical.